Ronald D. Vitiello, a veteran law enforcement official tapped by President Trump to run U.S. Immigration and Customs Enforcement, faced criticism at his Senate confirmation hearing Thursday for refusing to rule out the possibility that the Trump administration could resort again to separating migrant parents and children at the U.S.-Mexico border.

The White House is discussing plans to detain asylum-seeking families for up to 20 days and then give parents a choice: Stay in jail with their child pending a deportation hearing, or allow children to be taken to a government shelter so other relatives or guardians can seek custody of them.

“That option and that discussion is underway,” Vitiello told the Homeland Security and Governmental Affairs Committee. He would not address lawmakers’ questions seeking clarity on how long he believed migrant children should be detained or whether the separation from their familiescaused them psychological harm. “We’ll get less people bringing their children,” he added. “It is an option.”

Vitiello said that, for now, the president has ordered U.S. immigration officials to keep families together, but he said that detaining them all — or giving them the option to split up — could deter rising numbers of families seeking refuge at the Mexican border, including a caravan of mostly Hondurans that has infuriated the president.

The Trump administration has claimed that migrant families are filing false asylum claims to win release in the United States because the backlogged system does not have enough jail space or immigration judges to complete their cases quickly. Under current rules, officials cannot jail children with their parents for more than 20 days, which often forces the government to release the entire family into the United States.

Committee Democrats questioned Vitiello’s role in the administration’s widely criticized effort earlier this year to prosecute all parents who illegally crossed the border with their children. The policy split more than 2,500 children from their parents without a plan to reunite them before Trump stopped it in June. A federal court is still overseeing efforts to put all the families back together.

“We have the capacity in the United States of America to control our borders without harming children,” Sen. Maggie Hassan (D-N.H.) told Vitiello. “That is something that I am quite confident that we can do.”

Vitiello acknowledged during the hearing that the administration failed to be “ready for the public outcry that occurred.”

“We never contemplated on having the systems work backwards,” he said. “Nobody in the discussions that I was involved in were contemplating that these people would be separated forever.

“We’d like to be in a place where no one got separated,” Vitiello told Sen. Gary Peters (D-Mich.), but added, “We’d like to be in a place where lots of people didn’t bring their kids to the border and try to cross illegally, but that’s the situation we’re faced with now.”

Sen. Ron Johnson (R-Wis.), the committee’s chairman, dismissed criticism of Vitiello and other immigration agencies, saying they were merely enforcing the laws that Congress wrote.

“This is where Congress bears responsibility,” Johnson said. “. . . Right now, the law is broken.”

Vitiello presented himself as a career law-enforcement official who possesses the skills and political savvy to reach out to Democrats and Republicans alike, and to address rising concerns about the agency’s budget, detention conditions and polarizing reputation.

ICE is the Department of Homeland Security agency that detains and deports hundreds of thousands of immigrants a year for civil violations of immigration law. The agency also includes Homeland Security Investigations, a division that targets drug traffickers, gang members and other crime.

Since Trump took office, the agency has targeted people often treated more leniently under the Obama administration, including parents of American citizens and those without criminal records.

But Trump has also deported fewer immigrants each year than the Obama administration at its peak, partly because “sanctuary cities” are increasingly refusing to detain immigrants with little or no criminal history.

Vitiello insisted that the agency’s priority is deporting criminals and said he’d defend the agency against calls to abolish it.

“If confirmed, one of my highest priorities will be to better demonstrate to the public, Congress, and the media the importance and criticality of the mission to protect the homeland and improve public safety — and why our agency’s existence should not be up for debate,” he said.

Vitiello also acknowledged having made personal missteps, including a three-year-old tweet that compared Democrats to the Ku Klux Klan. In 2015, he tweeted from his personal account that the Democratic Party should be renamed the “Liberalcratic party or the NeoKlanist party,” according to the Gizmodo news site.

“It was a mistake,” he said. “It was a momentary lapse of judgment, and I apologize. It was meant as a joke.”

Vitiello, a 30-year Border Patrol veteran, is ICE’s acting director. Trump tapped him in August to replace Thomas D. Homan, the acting director whose nomination languished for months despite Republican control of the Senate.

Homeland Security Secretary Kirstjen Nielsen, whose tenure in the administration may be nearing its end, named Vitiello acting director in June, calling him “an experienced and well-respected career law enforcement officer who will be a strong advocate for the agency’s workforce.”

Vitiello has kept a lower profile than Homan, a lightning rod who praised Trump for taking the “handcuffs” off ICE and for rescinding policies that let millions of immigrants skirt deportation.

He also submitted multiple letters of support, including from R. Gil Kerlikowske, the U.S. Customs and Border Protection commissioner under President Barack Obama.

In his letter, Kerlikowske called Vitiello “an extremely effective, honest, and dedicated public servant” who led the Border Patrol’s effort to reduce uses of force in apprehending immigrants and introduced an internal affairs division to monitor the agency, whose secrecy has come under scrutiny.

“This would not have been possible without Mr. Vitiello’s leadership,” Kerlikowske wrote.

Vitiello, 55, is a Chicago native. He began his career with the Border Patrol in 1985 in Laredo, Tex., and has worked in leadership positions at Customs and Border Protection headquarters since 2010. Before joining ICE, he served as CBP’s acting deputy commissioner, helping the commissioner oversee 60,000 employees and a $13 billion budget.